Image Forming System and Image Forming Apparatus

ABSTRACT

An image forming system includes an image forming apparatus and a stacker that includes a discharged paper storage and a transporter, the discharged paper storage storing a sheet discharged from the image forming apparatus, and the transporter transporting the sheet to the discharged paper storage, wherein the image forming apparatus includes: an image former that forms an image on the sheet designated for a job and generates printed matter; and a hardware processor that performs control to cause the transporter to discharge a buffer sheet to the discharged paper storage, in which the printed matter is not discharged, before the job is executed, and that executes the job after the buffer sheet transported through the transporter is stored in the discharged paper storage to cause the transporter to transport the printed matter, which is generated by the image former, and cause the discharged paper storage to store the printed matter.

The entire disclosure of Japanese patent Application No. 2019-044474, filed on Mar. 12, 2019, is incorporated herein by reference in its entirety.

BACKGROUND Technological Field

The present invention relates to an image forming system and an image forming apparatus.

Description of the Related art

Conventionally, many sheets of paper discharged from an image forming apparatus are accumulated in a high-capacity stacker (hereinafter abbreviated as a “stacker”). The stacker is provided with a discharge tray for storing paper, and accumulates many sheets of paper discharged and stacked onto the discharge tray. In the discharge tray, grooves as well as bumps and dips of metal parts are formed to fit the shape of equipment that carries paper out of the stacker. For this reason, when the sheets of paper discharged from the image forming apparatus to the stacker are left for a long time, the weight of the bundle of paper accumulated in the discharge tray is added to the bottom sheet. This leaves a mark of the grooves or makes wrinkles on the sheet in contact with the discharge tray so that the sheet on which an image is formed (referred to as “printed matter”) is damaged.

When bulk printing is performed at a print shop. for example, a print job is kept running during the night hours or the like in which a user is absent. In addition, depending on the work procedure, printed matter may be left in the stacker while waiting for a next process of the printed matter. Thus, in order to buffer the effect of the discharge tray on the printed matter at the bottom of the bundle of paper, a user has manually placed a buffer plate or the like on the discharge tray before the image forming apparatus discharges the printed matter to the stacker.

JP 2007-169047 A states that “if a detection mechanism does not detect a sheet of paper when a plurality of sheets is discharged in bundle from a processing tray to a discharge tray. a sheet of paper is discharged onto the discharge tray, and then the sheets are discharged in bundle from the processing tray”.

However, if a user is not assigned near the stacker, the user cannot perform the operation of placing the buffer plate or the like on the discharge tray. Moreover, the method that relies on manual work is likely to result in a situation where the user forgets the operation or makes a mistake such as placing a plate or the like of an inappropriate size on the discharge tray. When a plate or the like of an inappropriate size is placed on the discharge tray a mark along the edges of the plate is left on the sheet at the bottom of the bundle of paper.

The technique disclosed in JP 2007-169047 A above has been made for the purpose of maintaining the alignment of the sheets on the discharge tray. Thus, when the bundle of paper discharged using the technique disclosed in JP 2007-169047 A is accumulated in the discharge tray for a long time, there is a high possibility that the printed matter at the bottom of the bundle of paper is damaged.

SUMMARY

The present invention has been made in view of such circumstances, and aims to protect printed matter stored in a stacker.

To achieve the abovementioned object, according to an aspect of the present invention, an image forming system reflecting one aspect of the present invention comprises an image forming apparatus and a stacker that includes a discharged paper storage and a transporter, the discharged paper storage storing a sheet discharged from the image forming apparatus, and the transporter transporting the sheet to the discharged paper storage, wherein the image forming apparatus includes: an image former that forms an image on the sheet designated for a job and generates printed matter; and a hardware processor that performs control to cause the transporter to discharge a buffer sheet to the discharged paper storage, in which the printed matter is not discharged, before the job is executed, and that executes the job after the buffer sheet transported through the transporter is stored in the discharged paper storage to cause the transporter to transport the printed matter, which is generated by the image former, and cause the discharged paper storage to store the printed matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The problems, advantages, configurations, effects and features provided by one or more embodiments of the invention will become more fully understood from the detailed description given hereinbelow and the appended drawings which are given by way of illustration only, and thus are not intended as a definition of the limits of the present invention:

FIG. 1 is a diagram of a schematic configuration of an image forming system according to an embodiment of the present invention;

FIG. 2 is a block diagram illustrating an example of an internal configuration of an image forming apparatus according to an embodiment of the present invention;

FIG. 3 is a block diagram illustrating an example of a hardware configuration of a computer according to an embodiment of the present invention;

FIG. 4 is a diagram of a structure of a table for buffer sheet discharge information according to an embodiment of the present invention;

FIG. 5 is a diagram of a structure of a table for feed tray designation information according to an embodiment of the present invention;

FIG. 6 is a diagram of a structure of a table for buffer sheet setting information according to an embodiment of the present invention;

FIG. 7 is an explanatory diagram illustrating a display example of a buffer sheet discharge setting screen according to an embodiment of the present invention;

FIG. 8 is an explanatory diagram illustrating a display example of a feed tray selection setting screen according to an embodiment of the present invention;

FIG. 9 is a flowchart illustrating an example of buffer sheet discharge determination processing according to an embodiment of the present invention;

FIG. 10 is a flowchart illustrating an example of processing in which a feed tray selection unit automatically selects a feed tray in step S7; and

FIG. 11 is a diagram of a structure of a table for buffer sheet discharge information according to a variation of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, one or more embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the disclosed embodiments. In the present specification and drawings, components having substantially the same function or configuration are denoted by the same reference numerals, and redundant description is omitted.

Embodiment Configuration of Image Forming System

First, an example of the configuration of an image forming system according to an embodiment of the present invention will be described with reference to FIG. 1.

FIG. 1 is a diagram of a schematic configuration of an image forming system 1 according to an embodiment of the present invention. Note that FIG. 1 illustrates elements considered necessary for the description of the present invention or related elements, and the image forming system of the present invention is not limited to the example illustrated in FIG. 1.

The image forming system 1 according to the present embodiment includes a paper feeder 2, an image forming apparatus 3, and a stacker 4.

The paper feeder 2 includes a plurality of feed trays 2 a (an example of a feed paper storage) that stores sheets Sh of different paper types to be fed to an image former 20 of the image forming apparatus 3. The feed trays 2 a store a large amount of the sheets Sh of different paper types and different sizes. However, the feed trays 2 a may store the sheets Sh of the same paper type and the same size. In the present embodiment, the sheet Sh to be fed to the image former 20 is stored in the feed tray 2 a of the paper feeder 2. The sheet Sh is an example of a recording material, and the image forming apparatus 3 can also form an image on a resin sheet that is an example of the recording material.

The sheet Sh set in the feed tray 2 a is fed to the image forming apparatus 3 at a predetermined timing. In the description of the present embodiment, the sheet Sh on which an image is formed and the sheet Sh discharged as a buffer sheet are both stored in the feed tray 2 a of the paper feeder 2, but these sheets Sh may be stored in a feed tray 14 of the image forming apparatus 3.

The image forming apparatus 3 is an example of an image forming apparatus that forms an image on the sheet Sh by electrophotography in which an image is formed using static electricity. The sheet Sh on which an image is formed is discharged to the stacker 4 as printed matter. The image forming apparatus 3 for example forms a color image on a sheet in a tandem form in which toner images of four colors being yellow (Y), magenta (M), cyan (C), and black (K) are superimposed. The image forming apparatus 3 is connected to a personal computer (PC) operated by a user, a print controller, and the like via a local area network (LAN) not shown. Then, a job is submitted from the PC or print controller to the image forming apparatus 3 via the LAN. The image forming apparatus 3 performs various processings such as image forming processing according to the job submitted.

The stacker 4 stores the sheet Sh discharged from the image forming apparatus 3 in a discharge tray 43 or 45 (an example of a discharged paper storage). The sheet Sh discharged to the stacker 4 is either the sheet Sh on which an image is formed by the image forming apparatus 3, or the sheet Sh fed from the feed tray 2 a and discharged as the buffer sheet. In the following description, the sheet Sh on which an image is formed by the image forming apparatus 3 is referred to as “printed matter”. Moreover, the sheet Sh that buffers the effect of an affecting part, such as a groove formed in the discharge tray 43. on the printed matter stored in the discharge tray 43 is referred to as the “buffer sheet”. The buffer sheet is a plurality of the sheets Sh stored at the bottom of the discharge tray 43 before the printed matter is discharged to the discharge tray 43 for the purpose of preventing damage to the printed matter. The buffer sheet may be of the same size and the same type as the sheet Sh being the printed matter, or may be of a different size and a different paper type therefrom. Moreover, as described later, one or a plurality of the sheets Sh may be discharged to the discharge tray 43 as the buffer sheet depending on the paper type. An image may also be formed on the sheet Sb used as the buffer sheet.

Here, an example of the internal configuration of the image forming apparatus 3 will be described also with reference to FIG. 1.

The image forming apparatus 3 includes an image input unit 11 having an auto document feeder (ADF) 12, and an operation display unit 13. The image forming apparatus 3 further includes a printer unit 10 having the feed tray 14 and the image former 20.

The image input unit 11 optically reads an image from a document on a document table of the ADF 12, and performs A/D conversion on the read image to generate image data. Note that the image input unit 11 can also read an image from a document on the platen glass.

The operation display unit 13 includes a display part formed of a liquid crystal panel or the like, and an operation part formed of a touch sensor or the like. The display part and the operation part are integrally formed as a touch panel, for example. The operation display unit 13 generates an operation signal indicating details of a user operation input to the operation part, and supplies the operation signal to a controller 30 (see FIG. 2 described later). Also, the operation display unit 13 displays details of a user operation, setting information, and the like on the display part on the basis of a display signal supplied from the controller 30. Note that the operation part can be formed of a mouse, a tablet, or the like to be formed separately from the display part.

The feed tray 14 (an example of the feed paper storage) is a container that stores the sheet Sh on which an image is formed by the image former 20. The feed trays 14 store sheets having different paper types, basis weights, and the like. Note that although the present embodiment illustrates an example in which two of the feed trays 14 are provided, the number of the feed trays 14 may be one, or may be three or more. Moreover, the feed tray 14 has a configuration similar to that of the feed tray 2 a for feeding the sheet Sh.

The image forming apparatus 3 is provided with a transport path 15 that transports the sheet Sh fed from any of the feed trays 2 a and 14 to the stacker 4 via the image former 20. The transport path 15 is provided with a plurality of transport rollers for transporting the sheet Sh.

The transport path 15 is extended and connected to a transport path 40 of the stacker 4 downstream of a fixing unit 26. The transport path 15 also branches off downstream of the fixing unit 26. One end of the transport path 15 being branched is connected to a reverse transport path 16 that joins the transport path 15 on the upstream side of the printer unit 10. The reverse transport path 16 is provided with a reversing unit 17 that reverses the sheet Sh. The sheet Sh reversed by the reversing unit 17 is returned to the upstream side of the transport path 15 through the reverse transport path 16. In some cases, the sheet Sh reversed by switching of the path is returned to the transport path 15 downstream of the fixing unit 26 and then discharged to the stacker 4.

The image former 20 forms an image on the sheet Sh designated for a job and generates printed matter. The image former 20 includes, for example, four image forming units 21Y, 21M, 21C, and 21K forming toner images of corresponding colors Y, M, C, and K, and forms an image on the sheet Sh transported through the transport path 15. No image is usually formed on the sheet Sb when the sheet Sh is used as the buffer sheet. However, the image former 20 may form, on the sheet Sh. an image serving as a mark for indicating to a user that the sheet is the buffer sheet.

The image forming units 21Y, 21M, 21C, and 21K include charging units, exposure units (all not shown), photosensitive drums 22Y, 22M, 22C, and 22K as image carriers, and developing units 23Y, 23M, and 23C, and 23K, respectively.

The developing units 23Y, 23M, 23C, and 23K irradiate surfaces (outer peripheral parts) of the corresponding photosensitive drums 22Y, 22M, 22C, and 22K with light according to images, thereby forming electrostatic latent images on the circumferences of the photosensitive drums 22Y, 22M, 22C, and 22K. Then, the developing units 23Y, 23M, 23C, and 23K form toner images on the photosensitive drums 22Y, 22M, 22C, and 22K by depositing toner to the electrostatic latent images.

The image former 20 further includes an intermediate transfer belt 24. a secondary transfer unit 25, the fixing unit 26, and an environment sensor 27. The intermediate transfer belt 24 is a belt onto which images formed on the photosensitive drums 22Y, 22M, 22C, and 22K are primarily transferred. The secondary transfer unit 25 is a roller that secondarily transfers the toner images of the respective colors, which have been primarily transferred onto the intermediate transfer belt 24, onto the sheet Sh transported through the transport path 15.

The fixing unit 26 is disposed downstream of the secondary transfer unit 25 along the sheet transport direction thereof and performs fixing processing on the sheet Sh which is supplied from the image former 20 and on which the color toner image is formed. The fixing unit 26 heats and pressurizes the sheet Sh being transported to fix the image transferred by the image former 20 on the front side of the sheet Sh. The sheet Sh on which the image is fixed by the fixing unit 26 is transported to the stacker 4 through the transport path 15, or is reversed by the reversing unit 17 through the reverse transport path 16 and then returned to the transport path 15 on the upstream side of the printer unit 10. When the sheet Sh is reversed, an image is formed on the back side of the sheet by the printer unit 10. After that, the sheet Sh is subjected to the fixing processing by the fixing unit 26 and transported to the stacker 4.

The environment sensor 27 detects temperature and/or humidity in the image forming apparatus 3 as information on the environment in the image forming apparatus 3. The temperature and humidity detected by the environment sensor 27 are output to the controller 30 (see FIG. 2 described later) of the image forming apparatus 3. Here, the image forming apparatus 3 need only include, as the environment sensor 27, at least one of a temperature sensor that detects only temperature and a humidity sensor that detects only humidity. Note that the environment sensor 27 may be provided inside the stacker 4 to detect the temperature and humidity in the stacker 4 and output the detected temperature and humidity to the controller 30.

Next, an example of the configuration of the stacker 4 will be described.

The stacker 4 accumulates the sheet Sh discharged from the image forming apparatus 3. The stacker includes transport paths 40, 42, and 44, a switching unit 41, the discharge trays 43 and 45, and a remaining paper sensor 46.

The transport path 40 is connected to the two transport paths 42 and 44 via the switching unit 41. The switching unit 41 switches the direction of transport of the sheet Sh such that the sheet Sh is transported to either one of the transport paths 42 and 44. The transport path 42 is connected to the discharge tray 43, and the transport path 44 is connected to the discharge tray 45. The transport path 42 discharges the sheet Sh to the discharge tray 43 when the sheet Sh is transported from the image forming apparatus 3 to the transport path 40, the sheet Sh being the printed matter on which an image is formed. Thus, in the present embodiment, the transport paths 40 and 42 of the stacker 4 are used as an example of a transporter. On the other hand, the transport path 44 discharges, to the discharge tray 45, the sheet Sh or the like on which an image is formed by a job different from a job for the sheet Sh that is discharged to the discharge tray 43. Note that the switching unit 41 is unnecessary if the stacker 4 has only one discharge tray 43.

The discharge tray 43 is lowered according to the number or weight of the sheets Sh accumulated. Thus, as the amount of the sheets Sh discharged increases, the discharge tray 43 gradually moving downward can store more of the sheets Sh. When a predetermined number or more of the sheets Sh are accumulated in the discharge tray 43, the operation of the image forming apparatus 3 is stopped, and the discharge of the sheets Sh to the discharge tray 43 is also stopped. After that, a user opens a front panel (not shown) provided to the stacker 4, takes out the sheet Sh from the discharge tray 43, and carries out the sheet.

In the present embodiment, a large amount of the sheets Sh on which images are formed by the image forming apparatus 3 are mainly discharged to the discharge tray 43 and stacked therein. On the discharge tray 43. affecting parts such as grooves and bumps and dips of metal parts are formed to affect the printed matter stored in the discharge tray 43. The affecting parts formed in the discharge tray 43 make it easier for a user to take out the printed matter from the stacker 4 even when the discharge tray 43 stores a large amount of printed matter.

The remaining paper sensor 46 is provided in the vicinity of the discharge tray 43. The remaining paper sensor 46 is used to detect the presence or absence of the sheet Sh (printed matter or buffer sheet) discharged to the discharge tray 43. Information regarding the presence or absence of the sheet Sh detected by the remaining paper sensor 46 is transmitted to the controller 30 (see FIG. 2 described later) of the image forming apparatus 3. The remaining paper sensor 46 may be an optical sensor capable of detecting the presence or absence of the sheet Sh by a change in intensity of reflected light of the light emitted toward the discharge tray 43, or may be a weight sensor capable of detecting the weight of the sheet Sh discharged to the discharge tray 43.

FIG. 2 is a block diagram illustrating an example of the internal configuration of the image forming apparatus 3.

The controller 30 that controls the internal operation of the image forming apparatus 3 includes a job reception unit 31, a paper presence/absence determination unit 32, a buffer sheet discharge determination unit 33, a feed tray selection unit 34, a buffer sheet discharge control unit 35, a mark formation instruction unit 36, and a job execution unit 37.

The job reception unit 31 receives a job from a PC or printer controller (not shown). The job received by the job reception unit 31 is temporarily saved in a storage 38, for example, and is read by the job execution unit 37 to be executed.

The paper presence/absence determination unit 32 determines the presence or absence of printed matter or a buffer sheet stored in the discharge tray 43. For example, the paper presence/absence determination unit 32 can determine whether or not the sheet Sh, that is, the printed matter or buffer sheet, is loaded in the discharge tray 43 on the basis of information input from the remaining paper sensor 46. A result of determination as to whether or not the sheet Sh is loaded is output to the buffer sheet discharge determination unit 33.

The buffer sheet discharge determination unit 33 determines whether or not to discharge the buffer sheet at the start of a job on the basis of the result of determination by the paper presence/absence determination unit 32 and buffer sheet discharge information 38 b in the storage 38. For example, the buffer sheet discharge determination unit 33 determines to allow for the discharge of the buffer sheet when the paper presence/absence determination unit 32 determines that neither the printed matter nor the buffer sheet is loaded in the discharge tray 43, and the buffer sheet discharge information 38 b indicates that a function of discharging the buffer sheet is enabled. In this case, the buffer sheet is discharged to the discharge tray 43 before the job is executed. The buffer sheet is preferably discharged between different jobs or after sheets accumulated in the discharge tray 43 are taken out, for example. The present embodiment uses the sheet Sh stored in the feed tray 2 a as an example of the buffer sheet, but a thin plate formed of resin or the like may be fed from the feed tray 2 a.

On the other hand, if the buffer sheet discharge information 38 b indicates that the function of discharging the buffer sheet is disabled, the buffer sheet discharge determination unit 33 determines that the buffer sheet cannot be discharged regardless of whether or not the sheet Sh is loaded in the discharge tray 43. Moreover, the buffer sheet discharge determination unit 33 determines that the buffer sheet need not be discharged when the paper presence/absence determination unit 32 determines that the printed matter or the buffer sheet has already been discharged to the discharge tray 43. The result of determination by the buffer sheet discharge determination unit 33 as to whether or not to discharge the buffer sheet is output to the feed tray selection unit 34.

The feed tray selection unit 34 selects the feed tray 2 a from which the buffer sheet is discharged on the basis of feed tray designation information 38 c in the storage 38, when the buffer sheet discharge determination unit 33 determines that the buffer sheet is to be discharged. When it is determined that the sheet Sh of the same size and type as the sheet Sh used as the printed matter is to be discharged as the buffer sheet as described above, the feed tray selection unit 34 selects the feed tray 2 a storing the sheet Sh on which an image of printed matter is formed. On the other hand, when the buffer sheet of a different size or different paper type from the sheet Sh being the printed matter is to be discharged, the feed tray selection unit 34 selects the feed tray 2 a different from the feed tray 2 a storing the sheet Sh on which an image of printed matter is formed.

Note that the sheet Sh that can be discharged as the buffer sheet may not be in the feed tray 2 a selected by the feed tray selection unit 34. In this case, the feed tray selection unit 34 acquires information such as free spinning of a pickup roller (not shown) provided in the feed tray 2 a, and determines that the feed tray 2 a selected has no sheet Sh that can be fed. Then, the feed tray selection unit 34 newly selects another one of the feed trays 2 a storing the sheet Sh that can be discharged as the buffer sheet. Details of the processing in which the feed tray selection unit 34 selects the feed tray 2 a will be described with reference to flowcharts illustrated in FIGS. 9 and 10 later.

The buffer sheet discharge control unit 35 performs control to discharge the buffer sheet through the transport path 42 to the discharge tray 43, in which the printed matter is not discharged, before a job is executed by the job execution unit 37. Here, the buffer sheet discharge control unit 35 performs control to discharge the buffer sheet when the paper presence/absence determination unit 32 determines that neither the sheet Sh nor the buffer sheet is stored in the discharge tray 43. Moreover, the buffer sheet discharge control unit 35 performs control to discharge, as the buffer sheet, the sheet Sh fed from the feed tray 2 a selected by the feed tray selection unit 34, when the buffer sheet discharge determination unit 33 determines to allow for the discharge of the buffer sheet. When the buffer sheet discharge control unit 35 performs control to discharge the sheet Sh from the feed tray 2 a as the buffer sheet, the pickup roller (not shown) or the like provided in the feed tray 2 a is driven to feed the sheet Sh from the feed tray 2 a selected. After that, the buffer sheet discharge control unit 35 receives information indicating the presence of the sheet Sh from the remaining paper sensor 46 to be able to determine that the buffer sheet has been discharged to the discharge tray 43.

The mark formation instruction unit 36 instructs the image former 20 and the job execution unit 37 to form an image, which serves as a mark for indicating to a user that the sheet Sh is the buffer sheet, on the sheet Sh discharged as the buffer sheet under the control of the buffer sheet discharge control unit 35. The mark formed on the buffer sheet can be an edge of the buffer sheet filled with a predetermined color. The color may fill, for example, a side of the buffer sheet corresponding to the side from which the buffer sheet discharged in the discharge tray 43 is taken out (the side of a front panel of the stacker 4), or another side of the sheet. When the buffer sheet is discharged to the discharge tray 43 with the edge thereof filled with the predetermined color as described above, a user can accurately determine at which position the buffer sheet is located and how may buffer sheets are discharged even if a large number of printed matter is thereafter stacked on the buffer sheet.

After the buffer sheet transported through the transport path 42 is stored in the discharge tray 43, the job execution unit 37 executes a rasterized job read from a job storage area 38 a of the storage 38 and causes the image former 20 to operate. Then, the job execution unit 37 causes the transport path 42 to transport the printed matter generated by the image former 20 and causes the discharge tray 43 to store the printed matter. Note that when the printer controller is not connected to the image forming apparatus 3, the job execution unit 37 can perform rasterization processing on a job read from the job storage area 38 a.

Moreover, when instructed by the mark formation instruction unit 36 to form a mark on the buffer sheet, the job execution unit 37 changes the order of execution of jobs such that the image former 20 forms the mark on the buffer sheet before the job is executed. As a result, the buffer sheet on which the mark is formed is discharged to the discharge tray 43 of the stacker 4, and then the sheet Sh on which the image former 20 has formed an image by the job execution unit 37 executing the job is discharged to the discharge tray 43. Note that when an instruction to form a mark on the buffer sheet is not input, the job execution unit 37 performs control on the image former 20 to discharge the sheet Sh used as the buffer sheet to the discharge tray 43 without forming an image on the sheet Sh.

The storage 38 includes the job storage area 38 a. The storage 38 also stores the buffer sheet discharge information 38 b, the feed tray designation information 38 c, and buffer sheet setting information 38 d.

A job received by the job reception unit 31 is stored in the job storage area 38 a to be read and executed as appropriate by the job execution unit 37. The job storage area 38 a stores a plurality of different jobs. Therefore, the job execution unit 37 can continuously execute a plurality of jobs read from the job storage area 38 a.

The buffer sheet discharge information 38 b is information that is set in advance by a user via the operation display unit 13, and is related to whether or not the buffer sheet can be discharged. The buffer sheet discharge information 38 b indicates that the function of discharging the buffer sheet under the control of the buffer sheet discharge control unit 35 is enabled or disabled according to the paper type of the sheet Sh designated for a job. For example, the sheet Sh having the paper type such as thick paper is less likely to have a mark caused by the affecting part of the discharge tray 43 and does not need the buffer sheet, in which case the function of discharging the buffer sheet is set to be disabled. On the other hand, the sheet Sh having the paper type other than thick paper is more likely to have a mark and needs the buffer sheet, in which case the function of discharging the buffer sheet is set to be enabled. Thus, the buffer sheet discharge determination unit 33 can determine whether or not the buffer sheet can be discharged with reference to the buffer sheet discharge information 38 b.

The feed tray designation information 38 c is information that is set in advance by a user via the operation display unit 13 and is related to the feed tray 2 a. The feed tray selection unit 34 refers to the feed tray designation information 38 c and selects the feed tray 2 a storing the sheet Sh to be discharged as the buffer sheet.

The buffer sheet setting information 38 d is information that is set in advance by a user via the operation display unit 13, and is related to discharge setting of the buffer sheet. The buffer sheet discharge control unit 35 refers to the buffer sheet setting information 38 d and determines the number of buffer sheets to be discharged according to the paper type and weight of the sheet Sb. The number of buffer sheets to be discharged is set to one or more.

Next, the hardware configuration of a computer 5 included in the image forming apparatus 3 will be described.

FIG. 3 is a block diagram illustrating an example of the hardware configuration of the computer 5.

The computer 5 is hardware used as a so-called computer. The computer 5 includes a central processing unit (CPU) 51, a read only memory (ROM) 52, and a random access memory (RAM) 53 each connected to a bus 54. The computer 5 further includes a display device 55, an input device 56, a non-volatile storage 57, and a network interface 58.

The CPU 51 reads, from the ROM 52, a program code of software that implements each function according to the present embodiment, loads the program code into the RAM 53, and executes the program code. In the RAM 53, variables, parameters, and the like generated during arithmetic processing of the CPU 51 are temporarily written, and these variables, parameters, and the like are read as appropriate by the CPU 51. Each functional unit included in the controller 30 in FIG. 2 is implemented by the CPU 51 executing a program.

The display device 55 is, for example, a liquid crystal display monitor and displays a result of processing performed by the computer 5 and the like to a user. The input device 56 includes a keyboard, a mouse, or the like, for example, where a user can perform predetermined operation input and instruction using the input device. In the present embodiment, a touch panel display in which the display device 55 and the input device 56 are combined is used as the operation display unit 13.

The non-volatile storage 57 includes, for example, a hard disk drive (HDD), a solid state drive (SSD), a flexible disk, an optical disc, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a non-volatile memory, or the like. The non-volatile storage 57 records a program that causes the computer 5 to function in addition to an operating system (OS) and various parameters. The ROM 52 and the non-volatile storage 57 permanently record programs, data, and the like necessary for the operation of the CPU 51, and are each used as an example of a non-transitory recording medium storing a computer-readable program executed by the computer 5.

The network interface 58 includes a network interface card (MC) or the like, for example, and various types of data can be transmitted and received between devices via a local area network (LAN), a dedicated line, or the like connected to a terminal of the NIC.

Example of Structure of Table for Buffer Sheet Discharge Information

FIG. 4 is a diagram of the structure of a table for the buffer sheet discharge information 38 b.

The buffer sheet discharge information 38 b is a table in which whether the function of discharging the buffer sheet is enabled or disabled is set in advance according to the paper type of the sheet Sh designated for a job executed by the job execution unit 37 (hereinafter referred to as the “present job”). The buffer sheet discharge information 38 b includes fields corresponding to the paper type of the present job and the discharge of the buffer sheet.

The field corresponding to the paper type of the present job stores the paper type of the sheet Sh designated for the present job. In the present embodiment, for example, airy one of thick paper, plain paper, and high-quality paper is designated.

The field corresponding to the discharge of the buffer sheet stores the setting of whether the discharge of the buffer sheet is enabled or disabled. For example, the sheet Sh whose paper type is thick paper is less prone to damage, so that the discharge of the buffer sheet is set to be disabled. When set to be disabled, the discharge of the buffer sheet is not performed. On the other hand, the sheet Sb whose paper type is plain paper or high-quality paper is prone to damage, so that the discharge of the buffer sheet is set to be enabled. When set to be enabled, the discharge of the buffer sheet is performed.

Example of Structure of Table for Feed Tray Designation Information

FIG. 5 is a diagram of the structure of a table for the feed tray designation information 38 c.

The feed tray designation information 38 c is a table in winch information on the feed tray 2 a storing the sheet Sh that can be discharged as the buffer sheet is set in an identifiable manner according to the paper type of the sheet Sh designated for the present job. The feed tray designation information 38 c includes fields corresponding to the feed tray, the paper type, the size, and the selection designation.

The field corresponding to the feed tray stores an identifier for identifying the feed tray 2 a that stores the sheet Sh as, for example, “A”, “B”, or “C”.

The field corresponding to the paper type stores, for each feed tray 2 a, the paper type of the sheet Sh stored in each feed tray 2 a. Examples of the paper type include plain paper and high-quality paper.

The field corresponding to the size stores the size of the sheet Sh stored in each feed tray 2 a. Examples of the size of the sheet Sh include A4 and B4.

The field corresponding to the selection designation stores information on the selection designation by a user as to whether or not the sheet Sh stored in the feed tray 2 a is discharged as the buffer sheet. For example; “yes” is stored under the selection designation field for the feed trays 2 a corresponding to “A” and “B”. No selection designation is made for the feed tray 2 a corresponding to “C”. Note that designation for the selection designation field is not essential. In some cases, no selection designation is made for all the feed trays 2 a.

Example of Structure of Table for Buffer Sheet Setting Information

FIG. 6 is a diagram of the structure of a table for the buffer sheet setting information 38 d.

The buffer sheet setting information 38 d is a table in which the number of the sheets Sh discharged to be used as the buffer sheets is set according to the paper type and the weight of the sheet Sh. The buffer sheet setting information 38 d includes fields corresponding to the paper type, the weight, and the number of buffer sheets discharged.

The field corresponding to the paper type stores the paper type of the sheet Sh that can be used as the buffer sheet. Examples of the paper type include plain paper and high-quality paper.

The field corresponding to the weight stores the weight [g/m²] for each paper type.

The field corresponding to the number of buffer sheets discharged stores the number of sheets that can be discharged as the buffer sheets for each paper type and weight of the sheet Sh. Typically, high-quality paper is better in quality and harder than plain paper. For this reason, the number of sheets to be discharged as the buffer sheets is set to be the same for high-quality paper and plain paper, or set to be less for high-quality paper than for plain paper.

Buffer Sheet Discharge Setting Screen

FIG. 7 is an explanatory diagram illustrating a display example of a buffer sheet discharge setting screen W1. The buffer sheet discharge setting screen W1 is a screen in which a user sets in advance the number of sheets of plain paper or high-quality paper to be discharged as the buffer sheets.

A user can operate the operation display unit 13 (an example of a discharge count setter) and set, in the storage 38, the number of the sheets Sh to be discharged as the buffer sheets through the buffer sheet discharge setting screen W1. Here, the user can operate the operation display unit 13 to set, in the storage 38, the number of sheets to be discharged according to the paper type and the weight of the sheet Sh. The buffer sheet discharge control unit 35 then performs control to discharge the set number of the sheets Sh as the buffer sheets.

Here, the buffer sheet discharge setting screen W1 includes a setting switch button W1 a and a discharge count setting area W1 b.

The setting switch button W1 a includes radio buttons that allow the setting to be switched between “batch setting” and “individual setting”. The “batch setting” is a button for the user to set that a preset number of the sheets Sh are discharged as the buffer sheets regardless of the paper type and the weight of the sheet. The “individual setting” is a button for the user to set the number of sheets according to the paper type and the weight of the sheet Sh. For example, when the radio button for the “individual setting” is selected, the user can set the number of sheets to be discharged in the discharge count setting area W1 b.

The discharge count setting area W1 b is an area for the user to individually set the number of sheets to be discharged according to the paper type and the weight of the sheet Sh used as the buffer sheet. For example, the sheet Sh whose paper type is plain paper or high-quality paper is used as the buffer sheet. The user can manually set the number of the sheets Sh discharged to be used as the buffer sheets while varying the number according to the paper type and the weight as illustrated in FIG. 6. The number of sheets to be discharged set for each paper type and weight in the discharge count setting area W1 b is stored in the buffer sheet setting information 38 d illustrated in FIG. 6.

Note that the buffer sheet discharge setting screen W1 may include a setting item for setting the total thickness of the buffer sheets discharged to the discharge tray 43 to a specified value or thicker. For example, when the total thickness is set to 5 mm or thicker, the buffer sheet discharge control unit 35 may automatically determine the total number of buffer sheets corresponding to the paper type of the sheet Sh such that the total thickness of the buffer sheets loaded equals 5 mm or thicker. Accordingly, a plurality of the sheets Sh can be used as the buffer sheets regardless of the paper type of the sheet Sh.

Moreover, the buffer sheet is more likely to have a wrinkle when the humidity in the image forming apparatus 3 and the stacker 4 rises, and the wrinkle may serve as a new affecting part to affect the printed matter. The buffer sheet discharge control unit 35 can thus perform control to discharge the buffer sheet by automatically increasing the number of buffer sheets discharged in accordance with the increase in the humidity in the image forming apparatus 3 detected by the environment sensor 27.

Feed Tray Selection Setting Screen

FIG. 8 is an explanatory diagram illustrating a display example of a feed tray selection setting screen W2. The feed tray selection setting screen W2 is a screen for setting the feed tray 2 a that stores the sheet Sh selected as the buffer sheet.

The feed tray selection setting screen W2 includes a setting switch button W2 a.

The setting switch button W2 a includes radio buttons that allow a user to switchably select the setting among “same tray”, “arbitrary”, and “automatic selection”.

When “same tray” is selected, the sheet Sh fed from the feed tray 2 a storing the sheet Sh on which a document image is formed is discharged as the buffer sheet. That is, the sheet Sh of the same paper type and weight as those of the sheet Sh on which a document image is formed is discharged as the buffer sheet.

When “arbitrary” is selected, the feed tray selection unit 34 selects the feed tray 2 a that is arbitrarily selected in advance from a plurality of the feed trays 2 a by the user. The buffer sheet discharge control unit 35 then performs control to discharge, as the buffer sheet, the sheet Sh fed from the feed tray 2 a selected by the feed tray selection unit 34. In this case, the sheet Sh of a different paper type or weight from that of the sheet Sh on which a document image is formed may be discharged as the buffer sheet.

The feed tray selection unit 34 selects another one of the feed trays 2 a when the sheet Sh is not stored in the feed tray 2 a selected. The buffer sheet discharge control unit 35 then performs control to discharge the sheet Sh fed from the other feed tray 2 a as the buffer sheet.

When “automatic selection” is selected, the sheet Sh fed from the feed tray 2 a that is automatically selected by the feed tray selection unit 34 is discharged as the buffer sheet. The feed tray selection unit 34 selects the feed tray 2 a storing the sheet Sh that call be used as the buffer sheet according to the paper type and weight of the sheet Sh on which an image is formed.

Note that one needs to prevent collapsing of a large number of printed matter stacked in the discharge tray 43. Thus, the feed tray selection unit 34 can select, from among the plurality of the feed trays 2 a, the feed tray 2 a storing the sheet Sh of the size (that is, the lengths along a main scanning direction and a sub scanning direction) larger than or equal to the size of the sheet Sh designated for a job. The buffer sheet discharge control unit 35 then performs control to discharge, as the buffer sheet, the sheet Sh fed from the feed tray 2 a selected.

FIG. 9 is a flowchart illustrating an example of buffer sheet discharge determination processing. The present processing assumes that a job received by the job reception unit 31 is stored in the job storage area 38 a of the storage 38. Then, the following processing is performed before the job execution unit 37 starts executing the job.

First, the paper presence/absence determination unit 32 acquires information on the presence/absence of the sheet Sh input from the remaining paper sensor 46, and determines whether the sheet Sh has been discharged to the discharge tray 43 (S1). In step S1, the paper presence/absence determination unit 32 may determine whether a predetermined number of the sheets Sh has been discharged to the discharge tray 43.

If the sheet Sh has already been discharged to the discharge tray 43 (YES in S1), the subsequent processing for discharging the buffer sheet is unnecessary so that the processing proceeds to step S9. On the other hand, if the sheet Sh has not been discharged to the discharge tray 43 (NO in S1), the buffer sheet discharge determination unit 33 refers to the buffer sheet discharge information 38 b illustrated in FIG. 2 and determines whether or not the buffer sheet discharge setting is enabled (S2). If the buffer sheet discharge setting is not enabled (NO in S2), that is, if the setting is disabled, the subsequent processing for discharging the buffer sheet is unnecessary so that the processing proceeds to step S9.

On the other hand, if the buffer sheet discharge setting is enabled (YES in S2). the feed tray selection unit 34 determines whether the feed tray 2 a storing the sheet Sh used as the buffer sheet is the same as the feed tray 2 a storing the sheet Sh designated for the present job to be executed (S3).

If it is determined that the feed trays 2 a are the same (YES in S3), the buffer sheet discharge control unit 35 performs control to discharge, as the buffer sheet, the sheet Sh fed from the feed tray 2 a that stores the sheet Sh designated for the present job, the feed tray being selected by the feed tray selection unit 34 (S4). Thereafter, the processing proceeds to step S8.

On the other hand, if it is determined that the feed trays 2 a are not the same (NO in S3), the feed tray selection unit 34 determines whether the selection designation for selecting the feed tray 2 a that stores the sheet Sh used as the buffer sheet has been made on the feed tray selection setting screen W2 (S5). If the selection designation for the feed tray 2 a has been made (YES in S5), the buffer sheet discharge control unit 35 performs control to discharge, as the buffer sheet, the sheet Sh fed from the feed tray 2 a designated to be selected (S6).

On the other hand, if the selection designation for the feed tray 2 a has not been made (NO in S5), the feed tray selection unit 34 refers to the feed tray designation information 38 c and automatically selects the feed tray 2 a storing the sheet Sh in accordance with the size of the sheet Sh designated for the job. The buffer sheet discharge control unit 35 then performs control to discharge, as the buffer sheet, the sheet Sh fed from the feed tray 2 a automatically selected (S7).

Here, the processing of step S7 will be described with reference to FIG. 10.

FIG. 10 is a flowchart illustrating an example of the processing in which the feed tray selection unit 34 automatically selects the feed tray 2 a in step S7.

First, the feed tray selection unit 34 selects an arbitrary one of the feed trays 2 a (S11). Next, the feed tray selection unit 34 determines whether the sheet Sh fed from the feed tray 2 a selected can be discharged as the buffer sheet (S12). If the sheet Sh can be discharged as the buffer sheet (YES in S12), the feed tray selection unit 34 determines whether the sheet Sh stored in the feed tray 2 a selected is of the same size as or larger than the sheet Sh designated for the present job (S13).

If the sheet Sh stored in the feed tray 2 a selected is of the same size as or larger than the sheet Sh designated for the present job (YES in S13), the buffer sheet discharge control unit 35 settles on the feed tray 2 a selected by the feed tray selection unit 34 and performs control to discharge the sheet Sh fed from the feed tray 2 a as the buffer sheet (S14). This completes the present processing, and the processing proceeds to step S8 in FIG. 9.

On the other hand, if it is determined in step S12 that the sheet Sh cannot be discharged as the buffer sheet (NO in S12), or if it is determined in step S13 that the sheet is smaller than the sheet Sh designated for the present job (NO in S13), the feed tray selection unit 34 determines whether there is a next feed tray 2 a (S15). For example, when the sheet Sh designated for the present job has size B4. the sheet Sh that can be discharged as the buffer sheet desirably has size B4 or larger. However, the sheet Sh stored in the feed tray 2 a with the identifier “A” in the feed tray designation information 38 c illustrated in FIG. 5 has size A4, whereby the sheet Sh cannot be discharged as the buffer sheet. In this case, the feed tray selection unit 34 continues the determination for the sheet Sh stored in the feed tray 2 a with the identifier “B” following the feed tray 2 a with the identifier “A”. If there is a next feed tray 2 a (YES in S15), the feed tray selection unit 34 returns to step S12 and continues the subsequent processing.

If determining in step S15 that there is no next feed tray 2 a (NO in S15), the feed tray selection unit 34 selects the feed tray 2 a that stores the sheet Sh designated for the present job. For example, in the feed tray designation information 38 c illustrated in FIG. 5, the feed tray 2 a storing the sheet Sh of size B4 has the identifier “B”. Therefore, the buffer sheet discharge control unit 35 performs control to discharge, as the buffer sheet, the sheet Sh fed from the feed tray 2 a (with the identifier “B”) that stores the sheet Sh designated for the present job (S16). This completes the present processing, and the processing proceeds to step S8 in FIG. 9.

Returning to step S8 of FIG. 9, the description of the processing will be continued.

After any of steps S4, S6, and S7, the buffer sheet discharge control unit 35 determines whether a set number of the buffer sheets has been discharged (S8). The number of buffer sheets discharged is stored in the storage 38 as a value obtained by the buffer sheet discharge control unit 35 counting the number of the sheets Sh discharged to be fed as the buffer sheets from the feed tray 2 a. Then, the buffer sheet discharge control unit 35 compares the number of the sheets Sh discharged to be fed as the buffer sheets, which is stored in the storage 38, with the number of sheets discharged in the buffer sheet setting information 38 d illustrated in FIG. 6. If the buffer sheet discharge control unit 35 determines that the set number of the buffer sheets has not been discharged (NO in S8), the processing returns to step S3 and the controller 30 repeats the processing.

If it is determined YES in step S1 or NO in step S2, or after the buffer sheet discharge control unit 35 determines in step S8 that the set number of buffer sheets has been discharged (YES in S8), the job execution unit 37 executes the present job and starts a printing operation (S9). After the present job is finished, the present processing is ended.

The image forming system 1 according to the embodiment described above discharges a plurality of the buffer sheets before discharging printed matter, when no printed matter is loaded in the discharge tray 43 of the stacker 4. Here, an, appropriate number of the buffer sheets is discharged according to the paper type and weight of the sheet Sh stored in the feed tray 2 a. As a result, the printed matter is stacked on the buffer sheets. Thus, even if a large number of the printed matter accumulated is left for a long time, the buffer sheets are deformed to prevent the affecting part formed in the discharge tray 43 from affecting the printed matter. The printed matter stored in the discharge tray 43 can be protected as a result.

The information 38 b to 38 d stored in the storage 38 can be changed by a user. Therefore, a value according to the paper type and the weight of the sheet Sh can be set appropriately. The user can also change the setting for the discharge of the buffer sheet. Thus, the sheet Sh fed from only a specific one of the feed trays 2 a may be discharged as the buffer sheet, or the sheet Sh fed from the feed tray 2 a that is automatically selected may be discharged as the buffer sheet.

The mark is formed on the edge of the buffer sheet discharged. A user can thus distinguish the printed matter from the buffer sheet correctly even if the printed matter and the buffer sheet discharged to the discharge tray 43 are of the same size.

Note that when the humidity in the stacker 4 increases, the sheet Sh discharged to the discharge tray 43 is likely to be wrinkled. Thus, the number of the sheets Sh discharged as the buffer sheets can be increased or decreased according to the humidity in the stacker 4. For example, the number of the buffer sheets can be increased if the humidity in the stacker 4 is higher than or equal to specified humidity, or the number of the sheets Sh can be maintained or decreased if the humidity is lower than the specified humidity

When the buffer sheet is stored in the discharge tray 43 while not overlapping the affecting part, the affecting part does not affect the printed matter stored in the discharge tray 43. Also, when the size of the sheet Sh discharged as the buffer sheet is smaller than the size of the printed matter, or depending on the orientation in which the buffer sheet is discharged, the affecting part is not located directly under the buffer sheet discharged in the discharge tray 43 and thus does not affect the buffer sheet and the printed matter. If the effect of the affecting part is small as described above, the first printed matter that is designated in a job executed by the job execution unit 37 and is stored first in the discharge tray 43 is less likely to be damaged. Thus, the buffer sheet discharge control unit 35 stops control for discharging the buffer sheet when the affecting part does not affect the printed matter stored in the discharge tray 43. That is, the printed matter is discharged to the discharge tray 43 without the buffer sheet being discharged. Note that when stopping the control for discharging the buffer sheet, the buffer sheet discharge control unit 35 may perform control to display, on the operation display unit 13, a message for prompting a user to perform resetting of the buffer sheet.

Moreover, when a user takes out the sheet Sh on which an image is formed from the discharge tray 43, checks the sheet Sh, and determines that the sheet Sh has a quality defect even though the buffer sheet is discharged, the user may input that the quality defect has occurred through the operation display unit 13. In this case, the setting is changed such that the number of the buffer sheets discharged in the buffer sheet setting information 38 d automatically increases. When a subsequent job is executed, a larger number of the buffer sheets is discharged to the discharge tray 43 so that no quality defect occurs on the sheet Sh on which an image is formed.

Moreover, depending on the paper type and the weight, the printed matter discharged in the discharge tray 43 may be less likely to have a wrinkle or mark without the buffer sheet. For this reason, when the job execution unit 37 executes a job, whether the discharge of the buffer sheet is enabled or disabled may be set depending on the paper type of the printed matter that is fed first from the feed tray 2 a.

Variation of Buffer Sheet Setting Information

Note that the buffer sheet discharge information 38 b may include settings for the influence of paper feed and the number of the buffer sheets discharged in addition to whether the function of discharging the buffer sheet is enabled or disabled as illustrated in FIG. 4.

FIG. 11 is a diagram of the structure of a table for buffer sheet discharge information 38 b 1.

The buffer sheet discharge information 38 b 1 is obtained by adding fields for the influence of paper feed and the number of the buffer sheets discharged to the fields of the buffer sheet discharge information 38 b illustrated in FIG. 4.

The field corresponding to the influence of paper feed stores the influence of paper feed according to the paper type of the sheet Sh designated for the present job. The influence of paper feed is an index that indicates a degree of the influence, such as a mark left on the sheet Sh at the bottom of a bundle of paper when the sheet Sh discharged as the printed matter is stacked in the discharge tray 43, and is expressed as relative values including “small”, “moderate”, and “large”. For example, when the paper type of the sheet Sb is thick paper, the discharge of the buffer sheet is set to be disabled so that there is no influence of paper feed. On the other hand, when the paper type of the sheet Sh of the present job is plain paper or high-quality paper, the influence of paper feed is any one of “small”, “moderate”, and “large”.

The field corresponding to the number of the buffer sheets discharged stores the number of the buffer sheets discharged according to the influence of paper feed. When the discharge of the buffer sheet is enabled, the number of the buffer sheets discharged increases as the influence of paper feed increases in the order of “small”, “moderate”, and “large”. When the influence of paper feed is “small”, the influence on the printed matter stacked on the buffer sheet is small even if the number of the buffer sheets is small. Thus, when the influence of paper feed is “small”, the number of the buffer sheets discharged is set to be small. Meanwhile, when the influence of paper feed is “large”, the printed matter stacked on the buffer sheet is more likely to have a mark if the number of the buffer sheets is small, whereby the influence on the sheet Sh is large. Thus, when the influence of paper feed is “large”, the number of the buffer sheets discharged is set to be large. When the influence of paper feed is “moderate”, the number of the buffer sheets discharged is set to roughly an intermediate value between the number of sheets discharged that is set when the influence of paper feed is “small” and the number of sheets discharged that is set when the influence of paper feed is “large”.

Note that when the discharge of the buffer sheet is disabled, the number of sheets discharged is set to zero.

By referring to the buffer sheet discharge information 38 b 1, the buffer sheet discharge control unit 35 can perform control to discharge the buffer sheets in number corresponding to the influence of paper feed. Various values under the field corresponding to the influence of paper feed and the field corresponding to the number of the buffer sheets discharged in the buffer sheet discharge information 38 b 1 can be set and changed by a user as appropriate.

Also, when the image forming apparatus 3 is used alone, the apparatus need only perform control to feed the sheet Sh from the feed tray 14 and discharge the printed matter, on which an image is formed by the image former 20, to the discharge tray that is attached to the image forming apparatus 3. In this case, only the transport path 15 of the image forming apparatus 3 is used as an example of the transporter, and one or a plurality of the buffer sheets being one or a plurality of the sheets Sh is discharged to the discharge tray.

Although embodiments of the present invention have been described and illustrated in detail, the disclosed embodiments are made for purposes of illustration and example only and not limitation, and can of course adopt various other application examples and variations without departing from the scope of the present invention described in the claims. The scope of the present invention should be interpreted by terms of the appended claims.

For example, the above embodiment describes the configurations of the apparatus and the system specifically and in details in order to provide a clear description of the present invention, and is not necessarily limited to one including all the configurations described. It is also possible to perform addition of another configuration, deletion, and/or replacement on a part of the configuration of each embodiment.

Furthermore, the control lines and information lines are those that are considered necessary for the description, and not all the control lines and information lines on the product are necessarily illustrated. In practice, one may consider that almost all the configurations are connected to one another. 

What is claimed is:
 1. An image forming system comprising an image forming apparatus and a stacker that includes a discharged paper storage and a transporter, the discharged paper storage storing a sheet discharged from the image forming apparatus, and the transporter transporting the sheet to the discharged paper storage, wherein the image forming apparatus includes: an image former that forms an image on the sheet designated for a job and generates printed matter; and a hardware processor that performs control to cause the transporter to discharge a buffer sheet to the discharged paper storage, in which the printed matter is not discharged, before the job is executed, and that executes the job after the buffer sheet transported through the transporter is stored in the discharged paper storage to cause the transporter to transport the printed matter, which is generated by the image former, and cause the discharged paper storage to store the printed matter.
 2. The image forming system according to claim 1, wherein the discharged paper storage includes an affecting part that affects the printed matter stored in the discharged paper storage, and the buffer sheet is one or a plurality of the sheets that buffers an effect of the affecting part on the printed matter stored in the discharged paper storage.
 3. The image forming system according to claim 2, wherein the hardware processor further determines whether or not the printed matter or the buffer sheet is stored in the discharged paper storage, and performs control to discharge the buffer sheet when determining that neither the printed matter nor the buffer sheet is stored in the discharged paper storage.
 4. The image forming system according to claim 2, further comprising a storage in which a function of discharging the buffer sheet by the hardware processor is set to be enabled or disabled, wherein the hardware processor further determines to allow for discharge of the buffer sheet when the function of discharging the buffer sheet is set to be enabled, and performs control to discharge the buffer sheet when making the determination to allow for discharge of the buffer sheet.
 5. The image forming system according to claim 2, further comprising a plurality of feed paper storages that each stores the sheet of a different paper type fed to the image former, wherein the hardware processor further selects the feed paper storage arbitrarily selected in advance from the plurality of feed paper storages, and performs control to discharge, as the buffer sheet, the sheet fed from the feed paper storage selected.
 6. The image forming system according to claim 5, wherein the hardware processor selects another one of the feed paper storages when the sheet is not stored in the feed paper storage selected, and performs control to discharge, as the buffer sheet, the sheet fed from the other one of the feed paper storages.
 7. The image forming system according to claim 5, wherein the hardware processor selects, from the plurality of feed paper storages, the feed paper storage that stores the sheet having the same size as or larger than the size of the sheet designated for the job, and performs control to discharge, as the buffer sheet, the sheet fed from the feed paper storage selected.
 8. The image forming, system according to claim 4, further comprising a discharge count setter that sets, in the storage, the number of the sheets discharged as the buffer sheets, wherein the hardware processor performs control to discharge the set number of the sheets as the buffer sheets.
 9. The image forming system according to claim 8, wherein the discharge count setter sets, in the storage, the number of the sheets discharged according to a paper type and weight of the sheet.
 10. The image forming system according to claim 8, further comprising a humidity sensor that detects humidity, wherein the hardware processor performs control to discharge the buffer sheet, the number of which is automatically increased according to an increase in the humidity detected by the humidity sensor.
 11. The image forming system according to claim 5, wherein the hardware processor stops the control of discharging the buffer sheet when the affecting part does not affect the printed matter stored in the discharged paper storage.
 12. The image forming system according to claim 11, wherein when the buffer sheet is stored in the discharged paper storage while not overlapping the affecting part, the affecting part does not affect the printed matter stored in the discharged paper storage.
 13. The image forming system according to claim 5, wherein the hardware processor stops the control of discharging the buffer sheet when the discharged paper storage has a little effect on a first sheet designated in the job executed by the hardware processor.
 14. The image forming system according to claim 5, wherein the hardware processor further instructs the image former to form an image, which serves as a mark of the buffer sheet, on the buffer sheet.
 15. An image forming apparatus comprising: a transporter that transports a sheet; a discharged paper storage that stores the sheet discharged by the transporter; an image former that forms an image on the sheet designated for a job and generates printed matter; a plurality of feed paper storages that stores the sheet fed to the image former; and a hardware processor that performs control to cause the transporter to discharge a buffer sheet to the discharged paper storage, in which the printed matter is not discharged, before the job is executed, and that executes the job after the buffer sheet transported through the transporter is stored in the discharged paper storage to cause the transporter to transport the printed matter, which is generated by the image former, and cause the discharged paper storage to store the printed matter. 